Frequency doubler

Abstract

Circuitry for doubling the frequency of a periodic input signal. The input periodic wave is applied to a differencing amplifier whose inputs are biased in such a manner that the output signal changes level twice during each half-cycle of the input periodic wave. This changing of level occurs at the same relative points in both half-cycles of the periodic input wave.

What is claimed is: 
     
       1. Circuitry for doubling the frequency of a periodic input signal comprising a differencing amplifier having a first input terminal, a second input terminal, and an output terminal, said amplifier providing a first signal at said output terminal when said first terminal has a greater applied signal level than said second terminal and providing a second signal at said output terminal when said second terminal has a greater applied signal level than said first terminal,   biasing means connected to said amplifier input terminals for providing a higher signal level to said second terminal than to said first terminal, said biasing means including a single voltage source,   a first resistor connected between said voltage source and said amplifier first input terminal, and   a second resistor connected between said voltage source and said amplifier second input terminal, said second resistor having a smaller resistance value than said first resistor, and     input means connected to said input terminals for increasing the signal level at said first terminal when said input signal is above a predetermined level and for decreasing the signal level at said second terminal when said input signal is below said predetermined level, said input means including means for receiving said input signal,   a first branch adapted to unidirectionally conduct current from said receiving means to said amplifier first input terminal when said input signal is above said predetermined level, and   a second branch adapted to unidirectionally conduct current from said amplifier second input terminal to said receiving means when said input signal is below said predetermined level.     
     
     
       2. The circuitry of claim 1 further including feedback means connected between said amplifier output terminal and said amplifier first input terminal, said feedback means increasing the signal level at said first input terminal when said first signal is present at said output terminal. 
     
     
       3. The circuitry of claim 1 wherein said first branch includes a first diode having its anode connected to said receiving means and its cathode connected to said amplifier first input terminal and said second branch includes a second diode having its cathode connected to said receiving means and its anode connected to said amplifier second input terminal. 
     
     
       4. Circuitry for doubling the frequency of a periodic input signal comprising a current differencing amplifier having a first input terminal, a second input terminal, and an output terminal, said amplifier providing a first signal at said output terminal when the current into said amplifier is greater at said first terminal than at said second terminal and providing a second signal at said output terminal when the current into said amplifier is greater at said second terminal than at said first terminal,   current providing means connected to said amplifier input terminals for providing more current to said amplifier at said second terminal than at said first terminal, said current providing means including a single voltage source,   a first resistor connected between said voltage source and said amplifier first input terminal, and   a second resistor connected between said voltage source and said amplifier second input terminal, said second resistor having a smaller resistance value than said first resistor, and     input means connected to said input terminals for providing current to said amplifier at said first terminal when said input signal is above a predetermined level and for drawing current from said amplifier at said second terminal when said input signal is below said predetermined level, said input means including means for receiving said input signal,   a first branch adapted to unidirectionally conduct current from said receiving means to said amplifier first input terminal when said input signal is above said predetermined level, and   a second branch adapted to unidirectionally conduct current from said amplifier second input terminal to said receiving means when said input signal is below said predetermined level.     
     
     
       5. The circuitry of claim 4 further including feedback means connected between said amplifier output terminal and said amplifier first input terminal, said feedback means increasing the current into said amplifier at said first input terminal when said first signal is present at said output terminal. 
     
     
       6. The circuitry of claim 4 wherein said first branch includes a first diode having its anode connected to said receiving means and its cathode connected to said amplifier first input terminal and said second branch includes a second diode having its cathode connected to said receiving means and its anode connected to said amplifier second input terminal.